When a pet starts acting funny, it can throw you into panic mode. Web site PetMD aims to help by supplying pet owners with the health knowledge they need for the pets they love.

The information is supplied via the health library, which has multiple sections: symptom center, learning center, topic center, breedopedia, vet dictionary, and emergency first aid. The site also offers—in addition to the abundance of pet health information—a finder service, helping you to locate emergency clinics, vets, groomers, pet day care, pet friendly hotels, pet parks, pet sitters, and pet walkers. And if you're looking to test your knowledge of fleas and ticks, check out the PetMD University courses.

With all the health and pet information supplied, PetMD aims to be your go-to resource for all things related to your pet. iPhone users can also purchase PetMD apps ($2) specific to various pet types in the iPhone App Store for on-the-go pet information.